A laminated glass made up of two glass plates with an interlayer film of plasticized polyvinyl butyral therebetween, all bonded together, has been widely used as window glass of automobiles, aircraft, architectures, and the like.
Interlayer films for a laminated glass may include a single resin layer, or may include a laminate of two or more resin layers. If an interlayer film includes, as the two or more resin layers, a first resin layer and a second resin layer which have different characteristics, the interlayer film can provide various properties that are difficult to achieve with interlayer films of a single layer.
For example, Patent Literature 1 discloses an interlayer film for a laminated glass including a sound insulating layer and two protective layers sandwiching the sound insulating layer. The sound insulating layer of the interlayer film for a laminated glass of Patent Literature 1 contains a polyvinyl acetal resin highly compatible with plasticizer and a large amount of plasticizer, thus providing excellent sound insulating properties. The protective layers, which sandwich the sound insulating layer, prevent the large amount of plasticizer in the sound insulating layer from bleeding out, thus preventing reduction of adhesion between the interlayer film and glass.
However, a laminated glass with such an interlayer film including a laminate of two or more resin layers may unfortunately cause ghost images when external rays of light are viewed through the glass. Such ghosting is pronounced especially in interlayer films for a laminated glass having excellent sound insulating properties, such as that of Patent Literature 1.